I just put the jpg images into a folder inside the pictures folder on the Kindle and they opened reasonably well with a few comics I tried. The only downside was that they weren't displayed full screen properly and were fairly dark. These were older comics with traditional white background and black images/text. Based on this, I didn't bother trying any newer comics, but I will now thanks to this thread.
I've not heard of mangle or canti, so thanks for the pointers.
